This invention relates to a screen assembly for collecting and discharging solid matter from a liquid-solid mixture in a waste stream. More particularly, it refers to a hydraulic drive assembly containing a stepping screen for lifting solids out of a waste water stream and depositing them in a solids repository.
It is well known in the prior art as shown in U.S. Pat. No. 4,853,116 to use a driving motor with an associated gear box propelling a pair of chains to move a grid structure upwardly and thereby lift solids out a liquid-solid mixture in a waste stream. Saw teeth are formed on combinations of displaceable bars and stationary bars to prevent the displaceable bars from becoming blocked. Such a system, while accomplishing its intended purpose, is cumbersome and unusually complex resulting in a high cost assembly of components. A more efficient and cost effective system is needed.
The present invention overcomes the deficiencies of the assembly described in U.S. Pat. No. 4,853,116 and provides an efficient cost effective means of removing solids from a liquid waste stream.
The invention is directed to an assembly of a grid structure surrounded by an outer frame with the assembly bottom portion located in a liquid waste stream containing solids. The grid structure includes multiple parallel alternate static and dynamic bars. Each bar has multiple vertically spaced apart shelves at a right angle to the vertical axis of the bar.
The dynamic bars have multiple spacers located on each side surface to space the dynamic bars from the static bars and support the horizontal displacement of the bars.
The outer frame on each side of the grid structure contains a pair of hydraulic cylinders connected to the dynamic bars by a shaft and mounting plate. One hydraulic cylinder of each pair causes the dynamic bars to move in a vertical plane and the other hydraulic cylinder of each pair causes the dynamic bars to move in a horizontal plane as dictated by a preprogrammed hydraulic system.
The grid structure moves solid material upwards and over the top of the grid structure to fall by gravity onto a conveyor for delivery of the solids to a waste receptacle. The liquid moves through the grid structure without impediment.